Source device detection

ABSTRACT

Methods, systems, and apparatuses are described for source device detection. Source device detection may be performed for a variety of types of connectors such as cables or board/substrate connectors across which a DC voltage or stable presence signal is normally supplied during connections when the power signal of the connector is not present. An alternating power source is coupled to a capacitor of known capacitance via a switch. The capacitor is in series with an effective capacitance of a sink device, a connector, and a source device. When the switch is open, the voltage between the capacitor and the effective capacitor is read to determine if a source device is present and On, and when closed, if the source device is present and Off or in Stand-By, or not present. The methods, systems, and apparatuses described include tunability for the capacitor based on temperature and effective capacitance variations.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationSer. No. 62/274,998, entitled “SOURCE DEVICE DETECTION,” filed on Jan.5, 2016, the entirety of which is incorporated by reference herein.

The present application is related to U.S. patent application Ser. No.14/945,125, filed Nov. 18, 2015, and entitled “AUTOMATIC IDENTIFICATIONAND MAPPING OF CONSUMER ELECTRONIC DEVICES TO PORTS ON AN HDMI SWITCH,”the entirety of which is incorporated herein by reference.

BACKGROUND

I. Technical Field

Embodiments described herein relate to source device detection andpresence.

II. Background Art

HDMI is one of the fastest growing interfaces for audio and videoconsumption in the world today. Commonly used HDMI enabled devices maybe classified as an HDMI Source: A device that sends an HDMI signal,such as a DVD player or Set-top box; an HDMI Sink: A device thatreceives an HDMI signal, such as an HDTV; and an HDMI Repeater: A devicethat both receives and sends HDMI signals, such as an A/V receiver. A/Vreceivers are considered HDMI repeaters.

BRIEF SUMMARY

Methods, systems, and apparatuses are described for source devicedetection and presence determinations, substantially as shown in and/ordescribed herein in connection with at least one of the figures, as setforth more completely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate embodiments and, together with thedescription, further serve to explain the principles of the embodimentsand to enable a person skilled in the pertinent art to make and use theembodiments.

FIG. 1 shows a block diagram of an HDMI system, according to an exampleembodiment.

FIG. 2 shows a block and circuit diagram of an HDMI system, according toexample embodiments.

FIG. 3 shows a block and circuit diagram of an HDMI system with apresence circuit, according to example embodiments.

FIG. 4 shows a block and circuit diagram of a presence circuit,according to an example embodiment.

FIG. 5 shows a flowchart for detecting source device presence, accordingto an example embodiment.

FIG. 6 shows a flowchart for detecting source device presence, accordingto an example embodiment.

FIG. 7 shows a flowchart for detecting source device presence, accordingto an example embodiment.

FIG. 8 shows a block and circuit diagram for determining an effectivecapacitance and setting a capacitor value, according to an exampleembodiment.

FIG. 9 shows graph for capacitive charge times, according to an exampleembodiment.

FIG. 10 shows a flowchart for tuning a first capacitor and determiningan effective capacitance, according to example embodiments.

FIG. 11 shows a flowchart for tuning a first capacitor and determiningan effective capacitance, according to example embodiments.

FIG. 12 shows a flowchart for tuning a first capacitor and determiningan effective capacitance, according to example embodiments.

FIG. 13 shows circuit diagrams of isolation circuits for isolatingvoltage sources for temperature and capacitance variations, according toexample embodiments.

FIG. 14 shows a flowchart for isolating voltage sources using isolationcircuits, according to example embodiments.

FIG. 15 shows a block diagram of a computing device/system in which thetechniques disclosed herein may be performed and the embodiments hereinmay be utilized.

Embodiments will now be described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

DETAILED DESCRIPTION I. Introduction

The present specification discloses numerous example embodiments. Thescope of the present patent application is not limited to the disclosedembodiments, but also encompasses combinations of the disclosedembodiments, as well as modifications to the disclosed embodiments.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In the discussion, unless otherwise stated, adjectives such as“substantially,” “approximately,” and “about” modifying a condition orrelationship characteristic of a feature or features of an embodiment ofthe disclosure, are understood to mean that the condition orcharacteristic is defined to be within tolerances that are acceptablefor operation of the embodiment for an application for which it isintended.

Furthermore, it should be understood that spatial descriptions (e.g.,“above,” “below,” “up,” “left,” “right,” “down,” “top,” “bottom,”“vertical,” “horizontal,” etc.) used herein are for purposes ofillustration only, and that practical implementations of the structuresdescribed herein can be spatially arranged in any orientation or manner.

Still further, it should be noted that the drawings/figures are notdrawn to scale unless otherwise noted herein.

Numerous exemplary embodiments are now described. Any section/subsectionheadings provided herein are not intended to be limiting. Embodimentsare described throughout this document, and any type of embodiment maybe included under any section/subsection. Furthermore, it iscontemplated that the disclosed embodiments may be combined with eachother in any manner. That is, the embodiments described herein are notmutually exclusive of each other and may be practiced and/or implementedalone, or in any combination.

II. Example Embodiments

The example techniques and embodiments described herein may be adaptedto various types of systems and devices, for example but withoutlimitation, HDMI-enabled devices, such as HDMI switches and/orrepeaters, communication devices (e.g., cellular and smart phones,etc.), computers/computing devices (e.g., laptops, tablets, desktops,etc.), computing systems, electronic devices, gaming consoles, homeelectronics and entertainment devices (e.g., home theater systems,stereos, televisions, media players, set top boxes, DVD players, etc.),and/or the like. It is contemplated herein that in various embodimentsand with respect to the illustrated figures of this disclosure, one ormore components described and/or shown may not be included and thatadditional components may be included. It is also contemplated hereinthat in various embodiments and with respect to the illustrated figuresof this disclosure, one or more components described and/or shown may beelectrically- and/or communicatively-coupled to other components inalternative and/or equivalent manners.

The embodiments and techniques described herein allow for source devicedetection, such as HDMI source device detection. HDMI has significantlyreduced the complexity of connecting multiple audio and video cablesbetween a source and a sink. An example system 100 is shown in FIG. 1.System 100 includes an HDMI switch 102, which is configured with one ormore HDMI input ports 120 and/or HDMI output ports 122. System 100 alsoincludes HDMI sourced devices: a first HDMI source 104, a second HDMIsource 106, and a third HDMI source 108; and one or more HDMI sinkdevices: illustrated as an HDMI sink 110. HDMI switch 102 is connectedto first HDMI source 104 via an HDMI connection 112, to second HDMIsource 106 via an HDMI connection 114, to third HDMI source 108 via anHDMI connection 116, and to HDMI sink 110 via an HDMI connection 118.HDMI connections as described herein may be embodied as HDMI cables orequivalent wired/wireless connectors. HDMI input ports 120 and/or HDMIoutput ports 122 may be dynamically configurable ports, in embodiments.That is, each of these ports may be configured as input or output portsbased on the type of HDMI device connected thereto.

HDMI switch 102 also includes a presence circuit 124. Presence circuit124 is configured to determine if an HDMI source device is present(i.e., a presence state) at a port of HDMI switch 102, e.g., one or moreHDMI input ports 120 and/or HDMI output ports 122, according toembodiments and as described herein. Presence circuit 124 is alsoconfigured to determine if an HDMI source device is powered on, is instand-by, or is powered off when present, which is also part of thepresence state according to embodiments. Presence circuit 124 may beconfigured to determine a presence state by utilizing a voltage dividercircuit (e.g., utilizing capacitive divider action) as described below.

In order to simplify user experiences for using multiple devices,multiport HDMI switch designs are envisioned as described in U.S. patentapplication Ser. No. 14/945,125, filed Nov. 18, 2015, and entitled“AUTOMATIC IDENTIFICATION AND MAPPING OF CONSUMER ELECTRONIC DEVICES TOPORTS ON AN HDMI SWITCH,” the entirety of which is incorporated hereinby reference. In accordance with the embodiments and techniquesdescribed herein, the proposed HDMI switch is configured with logic thatenables it to understand if an HDMI source device is connected to theHDMI switch or not.

The techniques and embodiments herein provide for novel devices,circuits, systems, and methods to detect presence/absence of an HDMIsource when interfaced with an HDMI sink using an HDMI cable. Forexample, according to embodiments, HDMI switch 102, acting as an HDMIsink, may be configured to detect when an HDMI source is connectedthereto, such as first HDMI source 104, second HDMI source 106, and/orthird HDMI source 108. Even though this system is explained in relationto an HDMI interface, the basic principles herein can be used to detectdevices on other interfaces like universal serial bus (USB), Ethernet,digital circuit connectors (HDMI switches, gaming consoles, televisions,set top boxes), in-line adapter connectors, etc., as well, according toembodiments.

In some embodiments, cable/connector lengths may be limited to 1 m, 2 m,or 5 m, although other lengths are contemplated herein. Cables andconnectors may carry data or embody data lines with DC or approximatelyDC characteristics, according to embodiments, such that the cables andconnectors do not introduce critical capacitance via highspeed/frequency issues.

In embodiments, the described detection techniques may be renderedinactive or idle when an HDMI device is detected and connected, and maybe active otherwise.

According to the HDMI Specification, +5V is provided by a source deviceover an HDMI connection (i.e., an HDMI cable) whenever the source deviceis connected to a sink device and is active or in an ON state. However,when +5V is not present on the HDMI connector of the sink, it can implythree different scenarios: 1) the source device is switched OFF; 2) thesource device is in standby; or 3) the HDMI cable between the sourcedevice and the sink device is disconnected.

The techniques and embodiments herein allow for identification of asource device if the source device is connected or not even when the +5Vsignal is not present. Accordingly, the techniques and embodimentsdescribed herein provide for improvements source device detection,including dynamic determinations of effective capacitances and tunablecapacitor values.

For instance, methods, systems, devices, and apparatuses are providedfor source device detection. A method in accordance with an exampleaspect is described. The method includes providing a voltage dividercircuit across a voltage associated with an HDMI port, and supplying afirst voltage to the voltage divider. The method also includes measuringa second voltage of the voltage divider based on the first suppliedvoltage, and determining a presence state of an HDMI source device basedat least on the second voltage that is measured.

A system in accordance with another example aspect is described. Thesystem includes an input port having an associated conductive element,the input port being configured to receive an HDMI connector for an HDMIsource device, and a voltage divider circuit across the associatedconductive element. The system also includes a signal source deviceconfigured to provide an electrical signal to the voltage dividercircuit, a voltage measurer configured to measure a voltage of thevoltage divider, and a determination component configured to determine apresence state of HDMI source devices based on the voltage of thevoltage divider.

A system in accordance with yet another example aspect is described. Thesystem includes a resistor-capacitor (RC) circuit that includes aresistor with a resistance and a capacitor with a capacitanceapproximately equal to combined capacitances of an HDMI sink devicecomprising the RC circuit, an HDMI source device, and an HDMI connectortherebetween, and a signal source device configured to provide anelectrical signal to the capacitor. The system also includes a voltagemeasurer configured to measure voltages of the capacitor while thecapacitor is charged by the electrical signal, and a determinationcomponent. The determination component is configured to determine aneffective value of the capacitance, and to set a divider capacitancevalue of a first voltage divider capacitor of a voltage divider circuitbased on the effective value, a second voltage divider capacitor of thevoltage divider circuit having a capacitance approximately equal to theeffective value.

Various example embodiments are described in the following Sections. Inparticular, example presence circuit embodiments are described. Thisdescription is followed by example tunable and effective capacitanceembodiments. Example isolation circuit embodiments are then provided.Next, further example embodiments and advantages are described, andsubsequently an example computing device implementation is described.Finally, some concluding remarks are provided. It is noted that thedivision of the following description generally into Sections and/orsubsections is provided for ease of illustration, and it is to beunderstood that any type of embodiment may be described in any Sectionor subsection.

III. Example Presence Circuit Embodiments

As noted above, systems, devices, and circuits for HDMI sourcedetection, such as circuits in an HDMI switch, along with theirrespective components such as presence circuits, may be configured invarious ways to determine HDMI source device presence states.

In embodiments, by way of illustrative example and not limitation, anHDMI switch or equivalent component may be configured to act as, and/orperform one or more functions of, an HDMI sink device. For instance, anHDMI switch may include one or ports that are configured to, or may bedynamically configured and mapped to, act as input ports for connectingHDMI source devices via connector cables. When a connector cable, e.g.,an HDMI cable, is connected to the port of the HDMI switch, there are anumber of presence state possibilities: 1) an HDMI source device isconnected to the other end of the connector and is powered on, 2) anHDMI source device is connected to the other end of the connector and isnot powered on or is in a stand-by or sleep mode, and 3) an HDMI sourcedevice is not connected to the other end of the connector (i.e., thereis not a device connected, or there is a connected device that is not anHDMI source device). The HDMI switch may determine the presence statebased on a presence circuit, such as presence circuit 124 of FIG. 1.

Referring to FIG. 2, a block and circuit diagram of an HDMI system 200(“system” 200) is shown, according to an embodiment. System 200 may be afurther embodiment of system 100 of FIG. 1. System 200 includes an HDMIsink device 202 (which may be an HDMI switch in embodiments), an HDMIsource device 204, and an HDMI cable 206 configured to connect HDMIsource device 204 to HDMI sink device 202. HDMI sink device 202 and HDMIsource device 204 may each include respective ports or connectors (e.g.,a port 216 and a port 218) into which HDMI cable 206 may be inserted tomake the connection therebetween. As shown in FIG. 2, between a +5V line220 and a ground plane/node 208 (“GND”) of system 200, there are threecapacitances that are connected in parallel: a capacitance Csource, acapacitance Ccable, and a capacitance Csink. For illustrative anddescriptive purposes, these capacitances are referred to herein asrealized “capacitors,” although it should be noted that one or morecomponents of the described systems and components may contribute toeach of the individual capacitances.

A capacitor Csink 210 is illustrated in HDMI sink device 202. Csink 210represents the capacitance between +5V line 220 and GND 208 of HDMI sinkdevice 202, e.g., but without limitation, on a printed circuit board(PCB) of HDMI sink device 202 or the like. Csink 210 has a capacitivevalue equivalent to the connective capacitance of HDMI sink device 202.

A capacitor Ccable 212 is illustrated in HDMI cable 206. Ccable 212represents the capacitance between +5V line 220 and GND 208 within HDMIcable 206. Ccable 212 has a capacitive value equivalent to theconnective capacitance of HDMI cable 206.

A capacitor Csource 214 is illustrated in HDMI source device 204.Csource 214 represents the capacitance between +5V line 220 and GND 208of HDMI source device 204, e.g., but without limitation, on a PCB ofHDMI source device 204 or the like. Csource 214 has a capacitive valueequivalent to the connective capacitance of HDMI source device 204.

As noted above, the techniques and embodiments herein allow forleveraging capacitive divider action, for example, between a known orpreviously measured capacitance and the capacitances as shown in system200 of FIG. 2. Subsequently, using associated voltage division, a clearlogic signal may be triggered for a microcontroller or processor, e.g.,of an HDMI sink/switch or computing/processing device as describedherein, to make a determination of an HDMI source presence state.

System 200 may also include a presence circuit 224 that may be anembodiment of presence circuit 124 of FIG. 1, as described in furtherdetail herein.

For instance, a block and circuit diagram of an HDMI system 300(“system” 300) is shown in FIG. 3, according to an embodiment. System300 may be a further embodiment of system 100 of FIG. 1 and/or system200 of FIG. 2. For instance, system 300 includes an HDMI sink device302, an HDMI source device 304, and HDMI cable 306, as similarlyprovided in system 200 of FIG. 2, as well as a GND 308 and a +5V line320, a capacitor Csink 310, a capacitor Ccable 312, and a capacitorCsource 314. System 300 also includes additional components in HDMI sinkdevice 202: a capacitor C1 322 (having a capacitance that may bepre-measured/pre-determined or dynamically determined), a switch 324,and a current source 326, which may collectively comprise at least aportion of a presence circuit 332. In embodiments, capacitor C1 302 iselectrically connected between Csink 310 and +5V line 320 by anelectrical connector 308. The output of current source 326 is providedvia an electrical connector 330 to switch 324, as shown, and C1 322 iselectrically connected to switch 324 via an electrical connector 328.

In embodiments, current source 326 may be an alternating current (AC)source, while in other embodiments current source 326 may be a digitalto analog converter (DAC), a clock source, or a voltage source, pairedwith zero or more additional circuit components (not shown), to providean equivalent circuit to that as illustrated in FIG. 3.

As noted, switch 324 may be electrically coupled between C1 322 andcurrent source 326. In embodiments, switch 324 is configured to open(i.e., be “off”) and close (i.e., be “on”) according to a control signalprovided via a control connector 334, described in further detailherein. When switch 324 is configured to be open, a present HDMI sourcedevice that is powered on causes a certain voltage to be held on +5Vline 320. When switch 324 is configured to be closed, a present HDMIsource device that is not in a powered-on state causes another voltageto be held on +5V line 320, and anon-present state causes yet anothervoltage to be held on +5V line 320, as described in further detailbelow.

For example, as noted above, capacitors representative of componentcapacitances, e.g., Csink 310, Ccable 312, and Csource 314, may comprisecapacitance values from one or more components of HDMI sink device 302,HDMI cable 306, and HDMI source device 304.

In embodiments, a capacitance value of C1 322 may be pre-selected ordynamically configured based on an effective capacitance value from thecombination of Csink 310, Ccable 312, and Csource 314, as describedherein. A capacitance value of C1 322 may be pre-selected or dynamicallyconfigured to have a capacitance value of approximately ten times thedescribed effective capacitance value of Csink 310, Ccable 312, andcapacitor Csource 314, although values greater or less than this arealso contemplated herein.

Accordingly, in system 300, C1 322 is connected in relation to Csink 310and current source 326 such that C1 322 forms a capacitor voltagedivider at the node between C1 322 and Csink 310 (i.e., at +5V line320). During operation when an HDMI source device (e.g., HDMI sourcedevice 304) is powered on and connected to HDMI sink device 302, +5Vline 320 carries a +5V signal in accordance with the HDMI specification.Based on the known or configured capacitance value of C1 322, and theeffective capacitance value of Csink 310, Ccable 312, and capacitorCsource 314, a presence state of an HDMI source device may be determinedaccording to the voltage value at +5V line 320 for presence statesincluding 1) an HDMI source device is connected to the other end of theconnector and is powered on, 2) an HDMI source device is connected tothe other end of the connector and is not powered on or is in a stand-byor sleep mode, and 3) an HDMI source device is not connected to theother end of the connector (i.e., there is not a device connected, orthere is a connected device that is not an HDMI source device), inembodiments.

The following are non-limiting examples to further illustrate theconfiguration of system 300 of FIG. 3. For example, values for Csink 310may be less than or equal to values for Csource 314 in embodiments.Ccable 312 may have a capacitance that is much smaller than that ofCsink 310 or Csource 314 and may be ignored for, or used in, most of thecalculations, techniques, and/or embodiments herein. Accordingly, inembodiments, if HDMI source device 304 is connected through HDMI cable306 to HDMI sink device 302, the capacitance of +5V line 320 will bedoubled (i.e., for capacitance values, if Csink 310 Csource 314),irrespective of the power status of HDMI source device 304. Thus, thetechniques and embodiments herein provide a way to identify the additionof capacitance on +5V line 320.

Referring still to FIG. 3 and the three components of presence circuit322, an example is provided. Current source 326 may be an AC voltagesource with a voltage V1 for purposes of the discussion below. Currentsource 326 may also output a square waveform or pulsating waveform. Inembodiments, a frequency of approximately 27 kHz-30 kHz may be used bycurrent source 326, although other frequencies are contemplated herein.Embodiments allow for tuning the source frequency for capacitance incables and/or connector circuits, as described herein. Additionally, inembodiments the voltage value may be a value less than or equal to thevoltage line value (e.g., a voltage value for +5V line 320 of +5V); insome example embodiments, a 3V value may be used. In some embodiments, aDAC output may be used as the source in lieu of current source 326.

C1 322 may be a known capacitor or a measured capacitor, or may comprisea capacitor bank that is dynamically tunable as described herein. Switch324 is configured to connect or disconnect current source 326 tocapacitor C1 322. Switch 324 may be controlled by a controller,processor, logic, and/or the like (not shown), according to a program,flowchart, state machine, etc., as contemplated herein and described infurther detail below.

In this example, switch 324 is in an off state (i.e., is open) when HDMIsource device 304 is powered ON and +5V is being provided thereby. WhenHDMI sink device 302 detects that the +5V is not present, then switch324 is closed or in an on state according to a control signal onconnector 334. When switch 324 is closed or in an on state, the ACvoltage V1 is divided between C1 322 and the effective capacitance ofCsink 310, Csource 314, and Ccable 312 (i.e., Ceff 416 as shown in FIG.4 and described below). In other words, switch 324 is open when HDMIsource device 304 is connected and powered on. If powered HDMI sourcedevice 304 is not detected by HDMI sink device 302, switch 324 is closedand C1 322 and the effective capacitance noted above form a voltagedivider based on current source 326.

The value of the effective capacitance (“Ceffective” below) of Csink310, Csource 314, and Ccable 312 may be different for differentscenarios, according to embodiments. For instance:

Case 1: When no HDMI source device 304 or HDMI cable 306 is connected toHDMI sink device 302, then: Ceffective (1)=Csink 310.

Case 2: When only HDMI cable 306 is connected to HDMI sink device 302,but HDMI source device 304 is not connected at the other end of HDMIcable 306, then: Ceffective (2)=Csink 310 in parallel to Ccable 312.

Case 3: When HDMI source device 304 is connected to HDMI sink device 302through HDMI cable 306, then: Ceffective (3)=Csink 310 in parallel toCcable 312 in parallel to Csource 314.

When HDMI cable 306 capacitance is very low, Ceffective (1) Ceffective(2). Thus, in such a scenario, if capacitors C1 322 and Csink 310 areappropriately selected, there will exist distinctly different voltagesat the junction (+5V line 320) between C1 322 and Csink 310 as shown inFIG. 3. This difference in voltage can then be used to identify thestate of connectivity, i.e., the presence state, of HDMI source device304.

Continuing with this example, let V1 be the effective voltage fromcurrent source 326. In this non-limiting example, V1=3V (averagevoltage), and let:

C1 322=10 nF;

Csink 310=10 nF;

Ccable 312=100 pF; and

Csource 314=100 nF.

According to Cases 1 and 2 above, the voltage at +5V line320≈V1×C1/(C1+Ceffective (1))=1.5V.

According to Case 3 above, the voltage at +5V line320=V1×C1/(C1+Ceffective (3))=0.25V.

As can clearly be seen from the values above, it is possible todistinctly differentiate between presence states when HDMI source device304 is connected to HDMI sink device 302, and when it is not.Measurement of voltage values at +5V line 320 may be performed inmultiple ways in embodiments (not shown, but described below), includingbut not limited to, 1) using an analog to digital converter (DAC) oranalog to digital convert (ADC) to monitor voltage changes, 2) usingsignal conditioning and level translation schemes to detect a high or alow voltage, and 3) using a voltage sensor or measurer such as avoltmeter and/or the like.

Additionally, according to embodiments, there are multiple algorithmscontemplated herein to identify the presence states of HDMI sourcedevices when the voltage at +5V line 320 can be distinctlydifferentiated for different states. It is also contemplated that statemachines may be used for state tracking. Algorithms and/or statemachines may be implemented in hardware, firmware, and/or software, orany combination thereof, and in conjunction with controllers or otherdetermination components.

It should be noted that other capacitor/current source configurationsare also contemplated herein. The example provided above is illustrativein nature, and is not to be considered limiting.

Referring also now to FIG. 4, a block and circuit diagram of a presencecircuit 400 is shown, according to an embodiment. Presence circuit 400may be a further embodiment of presence circuit 332 of system 300 ofFIG. 3. That is, presence circuit 400 includes a capacitor C1 402 (thatmay be pre-measured/pre-determined or dynamically determined), a switch404, and a current source 406, as similarly described with respect topresence circuit 332 of system 300 of FIG. 3, in embodiments. Presencecircuit 400 also includes a voltage measurer 408 and a controller 410.In embodiments, capacitor C1 402 is electrically connected betweenswitch 404, which is electrically coupled to a GND 412, and a capacitorCeff 416 (at a +5V line 414). The output of current source 406 isprovided via an electrical connector to switch 404.

C1 402 may be embodied as one or more capacitors. For example, in someconfigurations of presence circuit 400, C1 402 may be a single capacitorwith a capacitance selected based on known or estimated effectivecapacitance values of systems 200 or 300. In other configurations, C1402 may be a configuration of multiple capacitors and/or a capacitorbank illustrated as alternative C1 402 a. Alternative C1 402 a(capacitor bank) may comprise ‘n’ capacitors 424 a, 424 b, . . . , 424 nin one or more configurations (illustrated in a parallel configuration)to provide a variety of overall capacitive values. Capacitors 424 a, 424b, . . . , 424 n of alternative C1 402 a may be activated for useaccording to an activation signal on connector 420 that controlsactivators 418 a, 418 b, . . . , 418 n. The illustrated alternative C1402 a is exemplary and non-limiting in nature, and other capacitor bankconfigurations, including additional components or excluding illustratedcomponents, are contemplated herein. Additionally, the illustratedcomponents of alternative C1 402 a may arranged/configured in ways otherthan as shown (e.g., one or more of activators 418 a, 418 b, . . . , 418n may be placed on the opposite sides of their respective capacitors 424a, 424 b, . . . , 424 n, etc.).

Turning also to FIG. 5, a flowchart 500 for detecting source devicepresence is shown, according to an embodiment. Embodiments describedherein may be configured to perform source device detection according toflowchart 500. For instance, system 200 of FIG. 2, system 300 of FIG. 3and presence circuit 400, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 500. Flowchart 500 is describedas follows.

A voltage divider circuit is provided across a voltage associated withan HDMI port (502). For instance, Ceff 416 represents a capacitor and/orthe effective capacitance value of Csink 310, Ccable 312, and Csource314 of system 300 in FIG. 3, according to embodiments. C1 402 and Ceff416 form a voltage divider around their common node at +5V line 414,which may correspond to +5V line 320 and port(s) 316 of FIG. 3.

A first voltage is supplied to the voltage divider (504). For example,current source 406 (which may correspond to current source 326 of FIG.3) is configured to provide voltages to C1 402 by charging C1 402 viaswitch 404 when switch 404 is closed or “on.” Initially, controller 410may configure switch 404 to be open or “off” The first voltagecorresponds to no voltage associated with current source 406 for anelectrical signal being driven to C1 402 of the voltage divider due toswitch 404 being open, according to embodiments. That is, when switch404 is open, the voltage provided to the voltage divider corresponds tothe voltage supplied via the HDMI port (e.g., pert(s) 316) at +5V line414.

A second voltage of the voltage divider is measured based on the firstsupplied voltage (506). For instance, voltages at the common node of thevoltage divider (+5V line 414) are measured or sensed by voltagemeasurer 408. Voltage measurer 408 is configured to provide measuredvoltages, such as the second voltage, to controller 410. In embodiments,controller 410 is configured to provide control signals to switch 404based on voltages at +5V line 414 that are measured or sensed by voltagemeasurer 408. Controller 410 may base control signals on voltagesmeasured or sensed by voltage measurer 408 after a given time period ofmeasuring/sensing has elapsed in order to give C1 402 and/or Ceff 416sufficient time to charge from the electrical signal provided by currentsource 406 based on a timer 422.

A presence state of an HDMI source device is determined based at leaston the second voltage that is measured (508). For example, controller410 is configured to determine a presence state based on the voltagesmeasured or sensed by voltage measurer 408, such as the second voltagemeasured in (506). According to embodiments, determinations of presencestate are further based on the measured or sensed voltages and theconfiguration of switch 404 (i.e., open or closed). Controller 410 isalso configured to provide a logic signal via a connector 426 to amicrocontroller or processor, e.g., of an HDMI sink/switch orcomputing/processing device as described herein, to make a determinationof the HDMI source presence state or to perform other functions such asport mapping, etc. In some embodiments, controller 410 comprises suchmicrocontrollers or processors, or controller 410 may comprise aseparate controller or circuit, or may comprise software executing on amicrocontroller or processor, as described herein.

Referring also to FIG. 6, a flowchart 600 for detecting source devicepresence is shown, according to an embodiment. Embodiments describedherein may be configured to perform source device detection according toflowchart 600. For instance, system 200 of FIG. 2, system 300 of FIG. 3and presence circuit 400, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 600. Flowchart 600 may compriseadditional operations for flowchart 500 of FIG. 5. Flowchart 600 isdescribed as follows.

A third voltage is supplied to the voltage divider (602). Inembodiments, (602) may be performed after (506) and before (508) offlowchart 500. For example, based on the voltage measured in (506), oneor more additional operations may be performed beginning at (602).Switch 404 may be configured into a closed state by controller 410 basedon the voltage measured by voltage measurer in (506) when switch 404 isopen.

The supplied third voltage corresponds to the voltage associated withcurrent source 406, according to embodiments. The voltage associatedwith current source 406 may be less than +5V, between +5V and +3V, ormay be another value according to implementation-specific factors suchas communication protocol, device type, circuit configuration, and/orthe like. The voltage associated with current source 406 may correspondto an upper- and lower-bound between which current source 406 oscillatesor alternates (e.g., for sinusoidal sources, clock sources, DACs, etc.),and may comprise a direct current (DC) offset or bias voltage. Switch404 may be configured to be closed according to a control signal fromcontroller 410 to allow the electrical signal from current source 406 tobe provided to C1 402 of the voltage divider in (602).

A fourth voltage of the voltage divider is measured based on thesupplied third voltage (604). For instance, the supplied third voltagefrom current source 406 via closed switch 404 in (602) may charge C1 402of the voltage divider. After a determined or specified charging time,voltage measurer 408 measures or senses the voltage at the common nodeof the voltage divider between C1 402 and Ceff 416 (i.e., at +5V line414). Voltage measurer 408 is configured to provide measured voltages,such as the fourth voltage, to controller 410.

The presence state is determined based at least on the fourth voltagethat is measured (606). For example, controller 410 is configured todetermine a presence state based on the voltages measured or sensed byvoltage measurer 408, such as the fourth voltage measured in (604).According to embodiments, determinations of presence state are furtherbased on the measured or sensed voltages and the configuration of switch404 (i.e., open or closed). The presence state determined in (606) maybe included as a part of (508) in some embodiments.

An example embodiment with respect to system 300 and presence circuit400, and flowchart 500 and flowchart 600, will now be described. In thedescribed example, a current source with an associated voltage of +5Vand a capacitance value for C1 402 that is approximately 10 times thatof Ceff 416 are assumed. Additionally, comparison thresholds (forcomparing measured/sensed voltages in order to make presence statedeterminations) are assumed as +4V and +0.5V, although other thresholdsare contemplated herein.

Referring now to FIG. 7, a flowchart 700 for detecting source devicepresence is shown, according to an embodiment. Embodiments describedherein may be configured to perform source device detection according toflowchart 700. For instance, system 200 of FIG. 2, system 300 of FIG. 3,and presence circuit 400, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 700. Flowchart 700 may comprisean example embodiment of flowchart 500 of FIG. 5 and/or flowchart 600 ofFIG. 6. Flowchart 700 is described as follows.

Detection and presence determination is initiated (702). For instance,detection and presence determination may commence when an HDMI sinkdevice such as HDMI sink device 302 (which may be an HDMI switch)detects that an HDMI cable such as HDMI cable 306 has been plugged in orif the status of the cable or device thereon changes. Presence circuit400 of FIG. 4, when included in system 300 in HDMI sink device 302(which may be an HDMI switch) as an example, is configured to determinea presence state of an HDMI source device such as HDMI source device 304as noted herein.

The circuit switch is configured to be open (off) (704). For example,controller 410 of presence circuit 400 is configured to provide controlsignals to switch 404 to cause the configuration of switch 404 to beopen or off (if switch 404 is already open, it may remain so) such thatelectrical signals from current source 406 are not provided to C1 402 ofthe voltage divider circuit described in FIG. 4.

The voltage on the +5V voltage line in a voltage divider circuit ismeasured (706). In embodiments, voltage measurer 408 is configured tomeasure the common node between C1 402 and Ceff 416 (i.e., +5V voltageline 414), as described herein. The measured/sensed voltage value isprovided by voltage measurer 408 to controller 410.

If the measured voltage is ≧4V (708), the presence state is determinedby controller 410 as a source being present and powered on (710), andflowchart 700 returns to (704) above. That is, when switch 404 is open,and an HDMI source device is connected to an HDMI sink device, e.g., viaan HDMI cable as described herein, and the HDMI source device is poweredon, the HDMI source device will provide a +5V signal to the voltagedivider on +5V voltage line 414. Accordingly, the measured/sensedvoltage by voltage measurer 408 will be approximately +5V which isgreater than or equal to the +4V comparison threshold.

If the measured voltage is not ≧4V (708), flowchart 700 proceeds to(712). That is, when switch 404 is open and current source 406 does notprovide +5V to the voltage divider at C1 402, and the HDMI source deviceis either connected to the HDMI sink device but not powered on, or theHDMI source device is not connected, the HDMI source device will notprovide a +5V signal to the voltage divider on +5V voltage line 414.Accordingly, the measured/sensed voltage by voltage measurer 408 will beless than the +4V comparison threshold, and further operations may beperformed in order for controller 410 to determine the exact presencestate (as currently the intermediate determination would be that thereis not a connected and powered-on HDMI source device).

The circuit switch is configured to be closed (on) (712). For example,controller 410 of presence circuit 400 is configured to provide controlsignals to switch 404 to cause the configuration of switch 404 to beclosed or on such that electrical signals from current source 406 areprovided to C1 402 of the voltage divider circuit described in FIG. 4.As noted in (708) above, controller 410 has made an intermediatedetermination that there is not a connected and powered-on HDMI sourcedevice, and therefore, +5V voltage line 414 is not driven by an HDMIsource device. In such cases, controller 410 causes switch 404 to close(if switch 404 is already closed, it may remain so) and C1 402 ischarged by current source 406.

The voltage on the +5V voltage line in the voltage divider circuit ismeasured (714). In embodiments, voltage measurer 408 is configured tomeasure the common node between C1 402 and Ceff 416 (i.e., +5V voltageline 414), as described herein. In (714), the voltage measured byvoltage measurer 408 may be measured/sensed as C1 402 charges subsequentto switch 404 closing, or may be measured/sensed after a determined orspecified charging time has elapsed. In either case, a measured/sensedvoltage value is provided by voltage measurer 408 to controller 410.

If the measured voltage is ≦0.5V (716), the presence state is determinedby controller 410 as a source being present but not powered on (718),e.g., in an off or stand-by mode, and flowchart 700 returns to (712)above. That is, when switch 404 is closed, and an HDMI source device isconnected to an HDMI sink device, e.g., via an HDMI cable as describedherein, and the HDMI source device is not powered on, the HDMI sourcedevice will not provide a +5V signal, but rather will not drive thepower line and approximately 0V is provided to the voltage divider on+5V voltage line 414. Accordingly, when current source 406 provides a+5V signal via switch 404 to C1 402, the top plate of C1 402 receivingthe electrical signal will have a voltage value many times greater thanthe measured/sensed voltage by voltage measurer 408 will beapproximately 0V which is less than or equal to the +0.5V comparisonthreshold.

If the measured voltage is not ≦0.5V (716), it is then determined if themeasured voltage is ≧4V (720) by controller 410. If the measured voltageis not ≧4V (720), controller 410 determines that the presence state isthat an HDMI source device is not present (722), and flowchart 700returns to (712). If the measured voltage is ≧4V (720), flowchart 700returns to (704) where controller 410 may determine that the presencestate is that an HDMI source device is present and powered on (722)based on the voltage measured.

IV. Example Tunable and Effective Capacitance Embodiments

In embodiments, the top capacitor of voltage divider circuits describedherein, e.g., C1 402 of presence circuit 400 in FIG. 4, may beconfigured to predetermined capacitance values and/or may be dynamicallytunable as configurations of capacitor banks. Embodiments also providefor determining an effective capacitance, e.g., Ceff 416 as describedwith respect to FIG. 4.

Turning now to FIG. 8, a circuit 800 represented according to an exampleembodiment. Circuit 800 may be a further embodiment of presence circuit400 of FIG. 4, or may be a separate circuit.

Circuit 800 of FIG. 8 includes a capacitor 802 with capacitance C thatrepresents the effective capacitance of a line to be measured (analogousto Ceff 416 of FIG. 4). To initialize the determination of the effectivecapacitance for capacitor 802, a controller 814 may close a switch 808to provide an electrical path between a source 806 and a resistiveelement 804. With a known and stable source 806 (with an associatedvoltage Vs) electrically connected, and resistive element 804 with aknown resistance value (R) is in series with capacitor 802, bycalculating the time taken to charge capacitor 802 to different values(Vc), the effective capacitance “C” of capacitor 802 may be calculatedby controller 814 based on the voltage of capacitor 802 that ismeasured/sensed by a voltage measurer 812. Controller 814, with timer816, switch 808, and voltage measurer 812 may be further embodiments of,or similarly configured as, controller 414, with timer 422, switch 404,and voltage measurer 412 of FIG. 4 described above, and therefore, basicdescription of these components is not provided again here.

The time taken to reach the maximum voltage of capacitor 802 is definedby the equation:

Vc=Vs(1−ê ^((−t/RC))),  (Eq. 1)

where Vc is the voltage across capacitor 802, Vs is source 806 voltage,t is the elapsed charge time since the application of the supply voltagefrom source 806, and RC is a time constant based on the resistance valueR of resistive element 804 and the capacitance of capacitor 402. Time tmay be determined based on a timer 816 which may be configured to starttiming when switch 808 is closed by controller 814.

The relationship above in Equation 1 may be simplified to:

ln(1−(Vc/Vs))=−t/RC.  (Eq. 2)

As an example, if Vc=0.5 Vs, then ln(1−0.5)=−t/RC, or t=0.693 RC. Thisimplies that it takes 0.693 RC to reach 50% of the charging voltage ofcapacitor 802.

Referring also to FIG. 9, a timing graph 900 for capacitor charging isshown, according to an embodiment. Timing graph 900 shows capacitorvoltage 902 in volts (V) during charging (y-axis) with respect to time(t) (x-axis). At point 906, corresponding to time t2 and voltage V2, acapacitor, e.g., capacitor 802, is fully charged. V2 and t2 mayrespectively correspond to voltage Vc and time t of Equations 1 and 2above for a full capacitive charge. At point 904, corresponding to timet1 and voltage V1, the capacitor, e.g., capacitor 802, is 50% charged.Again, V1 and t1 may respectively correspond to voltage Vc and time t ofEquations 1 and 2 above for a 50% capacitive charge. That is, any amountor percentage of charge of a capacitor, and its corresponding time ofcharge, as shown by capacitor voltage 902, is contemplated herein foruse in the described embodiments.

Continuing with the examples describe above with respect to FIGS. 8 and9 in view of Equations 1 and 2 above, if the charging time (t) taken toreach 50% of the applied voltage Vs is known based on the capacitor sizeand type, then the capacitance value of the capacitor is:

C=t/0.693R.  (Eq. 3)

In this way, the effective capacitance of the line is calculated.

Also referring to FIG. 10, a flowchart 1000 for tuning a first capacitorand determining an effective capacitance is shown, according to anembodiment. Embodiments described herein may be configured to performsource device detection according to flowchart 1000. For instance,system 200 of FIG. 2, system 300 of FIG. 3, presence circuit 400, andcircuit 800 of FIG. 8, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 1000. Flowchart 1000 isdescribed as follows.

An electrical signal is provided to the capacitor (1002). For examplecontroller 814 is configured to provide a control signal to switch 808to place switch 808 in a closed configuration. An electrical signal isthen provided from source 806 to capacitor 804 through resistive element804. Capacitor 804 begins to charge based on the provided electricalsignal. Timer 816 may be configured to start timing when switch 808 isclosed by controller 814.

A voltage of the capacitor is measured while the capacitor is charged bythe electrical signal (1004). In embodiments, when charging commencesfor capacitor 802 as in (1002) above, voltage measurer 812 is configuredto measure or sense the voltage of capacitor 802 as it charges. In someembodiments, voltage measurer 812 is configured to measure or sense thevoltage of capacitor 802 as it charges at specific instances based ontiming values of timer 816. Voltage measurer 812 is also configured toprovide the measured/sensed voltage values to controller 814.

An effective value of the capacitance is determined (1006). Controller814 is configured to determine the effective capacitance value ofcapacitor 802. Also referring to FIG. 11, a flowchart 1100 for tuning afirst capacitor and determining an effective capacitance is shown,according to an embodiment. Embodiments described herein may beconfigured to perform source device detection according to flowchart1100. For instance, system 300 of FIG. 3, presence circuit 400, andcircuit 800 of FIG. 8, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 1100. Flowchart 1100 may be afurther embodiment of one or more operations of flowchart 1000 of FIG.10, such as (1006). Flowchart 1100 is described as follows.

The effective value is determined based on a representation of theeffective value after a charge time has elapsed (1102). Controller 814is also configured to determine the effective capacitance value ofcapacitor 802 based on the measured/sensed voltage values provided fromvoltage measurer 812 and the corresponding time from timer 816 at whichthe voltage value was measured/sensed, in embodiments. For instance,controller 814 may use this information, along with other known valuesassociated with circuit 800, e.g., the resistance value R and the sourcevoltage Vs, to determine the effective capacitance according toEquations 1, 2, and 3 above.

Referring again to flowchart 1000, a capacitance value of a firstvoltage divider capacitor of a voltage divider circuit is set based onthe effective value, a second voltage divider capacitor of the voltagedivider circuit having a capacitance approximately equal to theeffective value (1008). Setting the capacitance value of the firstvoltage divider capacitor of the voltage divider circuit may includedesign and manufacture aspects of HDMI switch/sink production, i.e., todetermine capacitance values and build products accordingly, or mayinclude dynamic tuning for HDMI switches/sinks during their operation.For example, capacitor 802 may represent, or may be, a capacitiveelement(s) representing the effective capacitance of connections in asystem or circuit (e.g., system 200 of FIG. 2, system 300 of FIG. 3,and/or presence circuit 400 of FIG. 4) such as, but not limited to Ceff416 of FIG. 4. An HDMI switch/sink device may be configured as describedherein to dynamically tune a capacitor of a presence circuit (e.g., C1402 of presence circuit 400 in FIG. 4) for implementation of a voltagedivider according to the effective capacitance value that is determined.In embodiments, with respect to C1 402 of presence circuit 400 in FIG. 4and circuit 800 of FIG. 8 as an illustrative, non-limiting example, acapacitor of a presence circuit that comprises the top portion of avoltage divider may be embodied as a capacitor bank, such as alternateC1 402 a of FIG. 4. Any number of capacitors of such a capacitor bank,e.g., 424 a, 424 b, . . . , 424 n, may be enabled for use to achieve anoverall capacitive value for the voltage divider according to anactivation signal on connector 420 from controller 410, or controller814, in embodiments.

Also referring to FIG. 12, a flowchart 1200 for tuning a first capacitorand determining an effective capacitance is shown, according to anembodiment. Embodiments described herein may be configured to performsource device detection according to flowchart 1200. For instance,system 200 of FIG. 2, system 300 of FIG. 3, presence circuit 400, andcircuit 800 of FIG. 8, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 1200. Flowchart 1200 may be afurther embodiment of one or more operations of flowchart 1000 of FIG.10, such as (1008). Flowchart 1200 is described as follows.

The divider capacitance value is set by configuring one or more of theplurality of bank capacitors, having a combined capacitance equal to atleast ten times the effective value, as usable by the voltage dividercircuit (1202). For instance, an activation signal on connector 420 fromcontroller 410, or controller 814, in embodiments, causes a specifiednumber of capacitors of alternate C1 204 a to be enabled for use toachieve an equivalent capacitance value approximately equal to 10 timesthe effective capacitance value determined for capacitor 802, althoughother equivalent capacitance values are also contemplated herein.

To improve the algorithm noted above in this Section, determinedcapacitive values can be verified for different charging voltages tore-verify the effective capacitance calculated. According toembodiments, this determination may be conducted to calculate aneffective capacitance of a system, such as system 200 of FIG. 2 and/orsystem 300 of FIG. 3, to confirm or set the capacitances for the topvoltage divider capacitors in presence circuits, e.g., C1 322 ofpresence circuit 332 in FIG. 3 or C1 402 (or alternate C1 402 a) ofpresence circuit 400 in FIG. 4, for the source detection techniques andembodiments as noted herein. In embodiments, the value of thesecapacitors (C1 322 and/or C1 402) may be 10 times the effectivecapacitance of the system, although other values are contemplated.Appropriate capacitor banks can be designed or utilized based onexperimentation and capacitors can be fine-tuned for the desired values.

Additionally, other equivalents may be used in embodiments such as, butnot limited to, an AC current source or other voltage source in place ofvoltage source 806 as shown, different components for net resistivityvalues may be used, and the placement of switch 808 may be varied withrespect to the components of circuit 800.

The tunable techniques and embodiments described herein may beimplemented in ways to account for variations in capacitance duringoperation for HDMI source devices, HDMI sink devices, and HDMI cables,dynamically and/or at the time of device connection.

V. Example Isolation Circuit Embodiments

Systems, devices, and circuits for HDMI source detection, such ascircuits in an HDMI switch like presence circuits, along with theirrespective components, may be configured in various ways to determineHDMI source device presence states, including utilizing circuitisolation, according to embodiments. In some implementations of thedescribed techniques and embodiments, such as during operation of HDMIdevices, improvements in operational performance and consistency areprovided using circuit isolation for temperature variances.

One problem with changes in temperature is associated with thecapacitance of voltage and current sources, such as clock sources (e.g.,AC voltage sources), and/or the like, as described herein. Changes incapacitance results in frequency drift for these sources and inincreases of power supply current for the sources. Cable detect schemesin accordance with HDMI such as the disclosed embodiments, are tolerablefor large amounts of drift in frequency, yet this tolerance is notlimitless. Additionally, as temperature increases in a system, problemsarise due to demand for current. As an example, a 555 based clock sourcerequires higher amounts of current as its associated temperatureincreases. When systems and circuits as described herein are unable todeliver higher amounts of current due to the temperature increase, theoutput voltage of sources such as reference clocks drops (e.g.,according to the voltage-to-current relationship) which results in falsecable detect scenarios and/or false presence state detection.

According to embodiments, the increase in demand of current noted aboveis compensated for by using isolation circuits comprising one or moretransistors in configurations to isolate sources such as voltage andcurrent sources without impacting the operation and performance of othersystems and circuits described herein. The example isolation circuitsdescribed below may comprise single transistor or Darlington pairtransistor configurations to isolate sources from the systems and/orcircuits described herein. It should be noted that while the describedisolation circuits include transistors, other equivalent circuitelements are also contemplated herein, as would be understood by one ofskill in the relevant art(s) having the benefit of this disclosure.

For example, FIG. 13 shows circuit diagrams of isolation circuits forisolating voltage sources for temperature and capacitance variations,according to embodiments. According to embodiments, transistors andtransistor pairs isolate the source and provides a consistent sourcevoltage at a wide range of temperatures for systems and circuitsdescribed herein. As illustrated, the transistors of FIG. 13 are BipolarJunction Transistors (BJTs), although other equivalent transistorsand/or elements are contemplated herein. A circuit 1302 and a circuit1304, each with single transistor configurations for isolation, and acircuit 1306 and a circuit 1308, each with Darlington pairconfigurations for isolation, are illustrated in FIG. 13. The isolationcircuits of FIG. 13 may be implemented in HDMI sink/switch devices, aswell as other HDMI and non-HDMI devices.

Circuit 1302, circuit 1304, circuit 1306, and circuit 1308 each includeelements common to each other that may be further embodiments ofportions of HDMI sink device 302 of FIG. 3 and/or of presence circuit400 of FIG. 4. That is, circuit 1302, circuit 1304, circuit 1306, andcircuit 1308 each include a capacitor C1 1342, a switch 1344, a source1346, a capacitor Csink 1348, a GND 1340, a +5V line 1350, which mayrespectively correspond to C1 322 of FIG. 3 and/or C1 402 of FIG. 4,switch 324 of FIG. 3 and/or switch 404 of FIG. 4, current source 326 ofFIG. 3 and/or current source 406 of FIG. 4, Csink 310 of FIG. 3 and/orCeff 416 of FIG. 4, GND 308 of FIG. 3 and/or GND 412 of FIG. 4, and +5Vline 320 of FIG. 3 and/or +5V line 414 of FIG. 4, according toembodiments. It should be noted that voltage and current sources may beimplemented interchangeably according to configurations and embodimentsas described herein, and that only Csink 1348 is shown for illustrativebrevity but that other components for an effective capacitance asdescribed herein are contemplated as being present in embodiments.

The described isolation circuits may be implemented with, or in placeof, the electrical connections between the outputs of sources (e.g.,source 1346) and switches (e.g., switch 1344) as shown. For instance,circuit 1302 also includes an isolation circuit 1352. Isolation circuit1352 includes an NPN transistor 1310 with its base electricallyconnected to the output of source 1346 via a resistive element 1312 witha resistance value R. The emitter of transistor 1310 is electricallyconnected to GND 1340, and the collector of transistor 1310 iselectrically connected to switch 1344 and to a system voltage VDD 1338via a resistive element 1314 having a resistance value R.

Circuit 1304 also includes an isolation circuit 1354. Isolation circuit1354 includes a PNP transistor 1316 with its base electrically connectedto the output of source 1346 via a resistive element 1318 with aresistance value R. The collector of transistor 1316 is electricallyconnected to GND 1340, and the emitter of transistor 1316 iselectrically connected to switch 1344 and to a system voltage VDD 1338via a resistive element 1320 having a resistance value R.

Circuit 1306 also includes an isolation circuit 1356. Isolation circuit1356 includes a Darlington pair comprising an NPN transistor 1330 and anNPN transistor 1332. The base of transistor 1330 is electricallyconnected to the output of source 1346 via a resistive element 1334 witha resistance value R. The emitter of transistor 1332 is electricallyconnected to GND 1340. The emitter of transistor 1330 is electricallyconnected to the base of transistor 1332, and the collectors oftransistor 1330 and transistor 1332 are electrically connected to switch1344 and to a system voltage VDD 1338 via a resistive element 1336having a resistance value R.

Circuit 1308 also includes an isolation circuit 1358. Isolation circuit1358 includes a Darlington pair comprising a PNP transistor 1322 and aPNP transistor 1324. The base of transistor 1322 is electricallyconnected to the output of source 1346 via a resistive element 1326 witha resistance value R. The collectors of transistor 1332 transistor 1324are electrically connected to GND 1340. The emitter of transistor 1322is electrically connected to the base of transistor 1324, and theemitter of transistor 1324 is electrically connected to switch 1344 andto a system voltage VDD 1338 via a resistive element 1328 having aresistance value R.

When the described isolation circuits are activated by source 1346, VDD1338 provides an electrical signal to switch 1344 and then to C1 1342 ifswitch 1344 is closed. Referring also to FIG. 14, a flowchart 1400 forisolating sources using isolation circuits is shown, according to anembodiment. Embodiments described herein may be configured to performsource device detection according to flowchart 1400. For instance,system 200 of FIG. 2, system 300 of FIG. 3, presence circuit 400,circuit 800 of FIG. 8, circuit 1302, circuit 1304, circuit 1306, andcircuit 1308 of FIG. 13, along with any respectivecomponents/subcomponents thereof, may be configured to perform sourcedevice detection according to flowchart 1400. Flowchart 1400 isdescribed as follows.

Isolate the voltage divider from temperature variations in the signalsource device (1402). For instance, isolation circuit 1352, isolationcircuit 1354, isolation circuit 1356, and isolation circuit 1358 areeach configured to isolate the voltage dividers described herein (e.g.,C1 322 and Csink 310 in FIG. 3 and/or C1 402 and Ceff 416 of FIG. 4)using transistors to prevent direct electrical connections andinteractions with sources of current/voltage that provide electricalsignals to the current dividers. Accordingly, variations in the outputof source 1346 do not affect the voltage dividers because an electricalsignal from VDD 1338 is provided thereto.

Provide a representation of the electrical signal to the voltagedivider, wherein the representation does not include temperature-inducedvariations of the signal source device (1404). For example, as notedabove, when the described isolation circuits are activated by source1346, VDD 1338 provides an electrical signal to switch 1344 via aconnected resistive element of circuit 1302, circuit 1304, circuit 1306,and circuit 1308 and then to C1 1342 when switch 1344 is closed. Thatis, the electrical signal from VDD 1338 is a representation or proxy ofthe output of source 1346 that is provided, according to the transistorconfigurations of circuit 1302, circuit 1304, circuit 1306, and circuit1308, based on the transistors being driven by the electrical signaloutput of source 1346.

VDD 1338 may be any system or device voltage such as, but not limitedto, an operating voltage. VDD 1338 may have a voltage value ofapproximately 3V-5V in some embodiments. Resistance values R forresistive elements described above may be the same or different,according to embodiments. Resistance values R may be determined based onspecific circuit implementations according to the value(s) of VDD 1338,transistor (or equivalent element) type, source characteristics such asvoltage, and/or the like.

VI. Further Example Embodiments and Advantages

As noted above, systems and devices may be configured in various ways todetect source devices for HDMI configurations, according to thetechniques and embodiments provided. For example, embodiments andtechniques, including methods, described herein may be performed invarious ways such as, but not limited to, being implemented by hardware,or hardware combined with one or both of software and firmware. Forexample, embodiments may be implemented as systems and devices, such asHDMI systems, schemes, setups, and devices, specifically customizedhardware, ASICs, FPGAs, mixed-signal circuits, logic and circuits on aprinted circuit board (PCB) (e.g., with discrete components) or a onsemiconductor substrate, other electrical circuitry, and/or the like.

In embodiments, a controller, such as controller 410 of FIG. 4 and/orcontroller 814 of FIG. 8, is configured to provide information regardingeffective capacitance values to a memory or storage device of an HDMIswitch and/or an HDMI sink for subsequent use in operations thereof.Such operation may include comparing subsequently detected effectivecapacitance values, when the HDMI source device is later connected, forrefining the techniques and embodiments described herein. For instance,after an effective capacitance value and a presence state aredetermined, an HDMI switch and/or an HDMI sink may identify a connectedHDMI source device that matches stored effective capacitance informationfor comparison of values.

Presence circuits such as presence circuit 400 and other circuits suchas circuit 800 described herein may be combined in embodiments. In suchcombinations, common components may be shared, and circuit-specificcomponents may be isolated from each other for individual operations ofthe described circuits using the described switches and/or additionalswitches not shown. It is also contemplated that multiple instances ofthe circuits described herein may be included in systems and devices,e.g., one instance for each port of a system or device).

Embodiments also provide for tuning capabilities to account fortemperature variations. As the temperature of a board such as a PCB of asystem or device increases due to internal/external factors, thecapacitance of a capacitor such as C1 322 of FIG. 3 and/or C1 402 ofFIG. 4 may be reduced. The amount of capacitance reduced depends uponmany factors such as dielectric material, temperature coefficient, etc.Referring again to FIG. 4, for example, reduction in capacitance maychange the ratio of C1 402 to Ceff 416 which in turn reduces thereference voltage of the circuit, and this may trigger a false cableconnect scenario. Additionally, capacitors with NPO dielectrics may beused, according to embodiments. Capacitors with NPO dielectrics havevery stable capacitance over a wide range of operating temperatures.This ensures that the ratio of C1 402 to Ceff 416 is more constant overwide temperature ranges, and hence reference voltage is not affected oris negligibly affected. In other words, in embodiments, an NPO capacitormay be used to stabilize the voltage divider portion of the circuitsdescribed herein.

In embodiments, one or more of the operations of any flowchart describedherein may not be performed. Moreover, operations in addition to or inlieu of any flowchart described herein may be performed. Further, inembodiments, one or more operations of any flowchart described hereinmay be performed out of order, in an alternate sequence, or partially(or completely) concurrently with each other or with other operations.

A “switch” as described herein with respect to circuits may be astandard switch, e.g., a single-pole, single-throw switch, etc., a fieldeffect transistor (FET) or other type of transistor, a multiplexor,combinatorial logic, and/or other equivalent components configured toselectively provide signals in a circuit.

A “connector,” as used herein, may refer to a hardware connection suchas an electrically conductive element or a software connection for thetransfer of data, instructions, and/or information, according toembodiments.

The further example embodiments and advantages described in this Sectionmay be applicable to embodiments disclosed in any other Section of thisdisclosure.

VII. Example Computer Implementations

Various features of the circuits, devices, and systems described herein,including but without limitation, system 200 of FIG. 2, system 300 ofFIG. 3, presence circuit 400 of FIG. 4, circuit 800 of FIG. 8, andcircuits 1302, 1304, 1306, and 1308 of FIG. 13, along with variousfeatures of any respective components/subcomponents thereof, and/or anytechniques, flowcharts, further systems, sub-systems, and/or componentsdisclosed and contemplated herein may be implemented in hardware (e.g.,hardware logic/electrical circuitry), or any combination of hardwarewith one or both of software (computer program code or instructionsconfigured to be executed in one or more processors or processingdevices) and firmware.

The embodiments described herein, including HDMI-enabled electronics,circuitry, devices, systems, methods/processes, and/or apparatuses, maybe implemented in or using well known processing devices, communicationsystems, servers, and/or, computers, such as a processing device 1500shown in FIG. 15. It should be noted that processing device 1500 mayrepresent communication devices/systems, entertainment systems/devices,HDMI-enabled devices, processing devices, as well as tablets, laptopsand/or traditional computers in one or more embodiments. For example,source device detection systems and devices according to the describedtechniques and embodiments, and any of the sub-systems and/or componentsrespectively contained therein and/or associated therewith, may beimplemented in or using one or more processing devices 1500 and similarcomputing devices.

Processing device 1500 can be any commercially available and well knowncommunication device, processing device, and/or computer capable ofperforming the functions described herein, such as, but not limited to,devices/computers available from International Business Machines®,Apple®, Sun®, HP®, Dell®, Cray®, Samsung®, Nokia®, etc. Processingdevice 1500 may be any type of computer, including a desktop computer, aserver, etc., and may be a computing device or system within anotherdevice or system.

Processing device 1500 includes one or more processors (also calledcentral processing units, or CPUs), such as a processor 1506. Processor1506 is connected to a communication infrastructure 1502, such as acommunication bus. In some embodiments, processor 1506 cansimultaneously operate multiple computing threads, and in someembodiments, processor 1506 may comprise one or more processors.

Processing device 1500 also includes a primary or main memory 1508, suchas random access memory (RAM). Main memory 1508 has stored thereincontrol logic 1524 (computer software), and data.

Processing device 1500 also includes one or more secondary storagedevices 1510. Secondary storage devices 1510 include, for example, ahard disk drive 1512 and/or a removable storage device or drive 1514, aswell as other types of storage devices, such as memory cards and memorysticks. For instance, processing device 1500 may include an industrystandard interface, such as a USB interface for interfacing with devicessuch as a memory stick. Removable storage drive 1514 represents a floppydisk drive, a magnetic tape drive, a compact disk drive, an opticalstorage device, tape backup, etc.

Removable storage drive 1514 may interact with a removable storage unit1516. Removable storage unit 1516 includes a computer useable orreadable storage medium 1518 having stored therein computer software1526 (control logic) and/or data. Removable storage unit 1516 representsa floppy disk, magnetic tape, compact disk, DVD, optical storage disk,or any other computer data storage device. Removable storage drive 1514reads from and/or writes to removable storage unit 1516 in a well-knownmanner.

Processing device 1500 also includes input/output/display devices 1504,such as touchscreens, LED and LCD displays, monitors, keyboards,pointing devices, etc.

Processing device 1500 further includes a communication or networkinterface 1520. Communication interface 1520 enables processing device1500 to communicate with remote devices. For example, communicationinterface 1520 allows processing device 1500 to communicate overcommunication networks or mediums 1522 (representing a form of acomputer useable or readable medium), such as LANs, WANs, the Internet,etc. Communication interface 1520 may interface with remote sites ornetworks via wired or wireless connections.

Control logic 1528 may be transmitted to and from processing device 1500via the communication medium 1522.

Any apparatus or manufacture comprising a computer useable or readablemedium having control logic (software) stored therein is referred toherein as a computer program product or program storage device. Thisincludes, but is not limited to, processing device 1500, main memory1508, secondary storage devices 1510, and removable storage unit 1516.Such computer program products, having control logic stored thereinthat, when executed by one or more data processing devices, cause suchdata processing devices to operate as described herein, representembodiments.

Techniques, including methods, and embodiments described herein may beimplemented by hardware (digital and/or analog) or a combination ofhardware with one or both of software and/or firmware. Techniquesdescribed herein may be implemented by one or more components.Embodiments may comprise computer program products comprising logic(e.g., in the form of program code or software as well as firmware)stored on any computer useable medium, which may be integrated in orseparate from other components. Such program code, when executed by oneor more processor circuits, causes a device to operate as describedherein. Devices in which embodiments may be implemented may includestorage, such as storage drives, memory devices, and further types ofphysical hardware computer-readable storage media. Examples of suchcomputer-readable storage media include, a hard disk, a removablemagnetic disk, a removable optical disk, flash memory cards, digitalvideo disks, random access memories (RAMs), read only memories (ROM),and other types of physical hardware storage media. In greater detail,examples of such computer-readable storage media include, but are notlimited to, a hard disk associated with a hard disk drive, a removablemagnetic disk, a removable optical disk (e.g., CDROMs, DVDs, etc.), zipdisks, tapes, magnetic storage devices, MEMS (micro-electromechanicalsystems) storage, nanotechnology-based storage devices, flash memorycards, digital video discs, RAM devices, ROM devices, and further typesof physical hardware storage media. Such computer-readable storage mediamay, for example, store computer program logic, e.g., program modules,comprising computer executable instructions that, when executed by oneor more processor circuits, provide and/or maintain one or more aspectsof functionality described herein with reference to the figures, as wellas any and all components, capabilities, and functions therein and/orfurther embodiments described herein.

Such computer-readable storage media are distinguished from andnon-overlapping with communication media, software programs, andtransitory signals (do not include communication media, softwareprograms, or transitory signals). Communication media embodiescomputer-readable instructions, data structures, program modules orother data in a modulated data signal such as a carrier wave. The term“modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia includes wireless media such as acoustic, RF, infrared and otherwireless media, as well as wired media and signals transmitted overwired media. Embodiments are also directed to such communication media.

The techniques and embodiments described herein may be implemented as,or in, various types of devices. For instance, embodiments may beincluded, without limitation, in processing devices (e.g., illustratedin FIG. 15) such as computers and servers, as well as communicationsystems such as switches, routers, gateways, and/or the like,communication devices such as smart phones, home electronics, gamingconsoles, entertainment devices/systems, etc. A device, as definedherein, is a machine or manufacture as defined by 35 U.S.C. §101. Thatis, as used herein, the term “device” refers to a machine or othertangible, manufactured object and excludes software and signals. Devicesmay include digital circuits, analog circuits, or a combination thereof.Devices may include one or more processor circuits (e.g., centralprocessing units (CPUs), processor 1506 of FIG. 15), microprocessors,digital signal processors (DSPs), and further types of physical hardwareprocessor circuits) and/or may be implemented with any semiconductortechnology in a semiconductor material, including one or more of aBipolar Junction Transistor (BJT), a heterojunction bipolar transistor(HBT), a metal oxide field effect transistor (MOSFET) device, a metalsemiconductor field effect transistor (MESFET) or other transconductoror transistor technology device. Such devices may use the same oralternative configurations other than the configuration illustrated inembodiments presented herein.

VIII. Conclusion

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. It will be apparent to persons skilled in the relevant artthat various changes in form and detail can be made therein withoutdeparting from the spirit and scope of the embodiments. Thus, thebreadth and scope of the embodiments should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. A method comprising: providing a voltage dividercircuit across a voltage associated with an HDMI port; supplying a firstvoltage to the voltage divider; measuring a second voltage of thevoltage divider based on the first supplied voltage; and determining apresence state of an HDMI source device based at least on the secondvoltage that is measured.
 2. The method of claim 1, wherein the firstvoltage is approximately 0V, wherein the measured second voltage isgreater than, or greater than or equal to, approximately 4V, and whereinthe presence state is indicative of an HDMI source device being presentand being powered on.
 3. The method of claim 1, further comprising:supplying a third voltage to the voltage divider; measuring a fourthvoltage of the voltage divider based on the second supplied voltage; anddetermining the presence state based at least on the fourth voltage thatis measured.
 4. The method of claim 3, wherein the third voltage isbetween approximately 3V and 5V, wherein the measured fourth voltage isless than, or less than or equal to, approximately 0.5V, and wherein thepresence state is indicative of an HDMI source device being present. 5.The method of claim 3, wherein the third voltage is betweenapproximately 3V and 5V, wherein the measured fourth voltage is greaterthan, or greater than or equal to, approximately 4V, and wherein thepresence state is indicative of an HDMI source device not being present.6. The method of claim 3, wherein the third voltage is supplied by oneof a current source or a voltage source via a circuit switch that iselectrically coupled between a current divider and the current source,and is configured to be closed to provide an electrically conductivepath to supply the third voltage.
 7. The method of claim 1, wherein thevoltage divider circuit comprises a first capacitor and a secondcapacitor, wherein the second capacitor is configured to have aneffective capacitance approximately equal to combined capacitances of anHDMI sink device comprising the voltage divider circuit, the HDMI sourcedevice, and an HDMI connector therebetween, and wherein the firstcapacitor has a pre-configured capacitance equal to at leastapproximately ten times the effective capacitance.
 8. The method ofclaim 1, wherein the voltage divider circuit comprises a first capacitorand a second capacitor, wherein the second capacitor is configured tohave an effective capacitance approximately equal to the combinedcapacitances of an HDMI sink device comprising the voltage dividercircuit, the HDMI source device, and an HDMI connector therebetween, andwherein the first capacitor is configured to be dynamically tunable tohave a capacitance equal to at least approximately ten times theeffective capacitance.
 9. A system comprising: an input port having anassociated conductive element, the input port being configured toreceive an HDMI connector for an HDMI source device; a voltage dividercircuit across the associated conductive element; a signal source deviceconfigured to provide an electrical signal to the voltage dividercircuit; a voltage measurer configured to measure voltages of thevoltage divider; and a determination component configured to determine apresence state of HDMI source devices based on the voltage of thevoltage divider.
 10. The system of claim 9, wherein the signal sourcedevice is one of a current source, a digital to analog converter, aclock source, or a voltage source; and wherein the voltage dividercomprises a first capacitor, and a second capacitor that has aneffective capacitance approximately equal to combined capacitances of anHDMI sink device comprising the voltage divider circuit, the HDMI sourcedevice, and the HDMI connector therebetween.
 11. The system of claim 10,wherein one or more of the first capacitor and the second capacitorcomprise a negative-positive zero (NPO) dielectric.
 12. The system ofclaim 9, further comprising: a circuit switch electrically coupledbetween the signal source device and the voltage divider, the circuitswitch being configured to: open and close based on an activation signalfrom the determination component; and allow the voltage measurer tomeasure at least two different voltages of the voltage divider that arebased on the electrical signal and on the absence of the electricalsignal.
 13. The system of claim 12, wherein the determination componentis configured to: determine the presence state as being indicative of anHDMI source device being present and being powered on based on a voltagevalue measured by the voltage measurer when the circuit switch is open.14. The system of claim 12, wherein the determination component isconfigured to: determine the presence state as being indicative of anHDMI source device being present based on a voltage value measured bythe voltage measurer when the circuit switch is closed.
 15. The systemof claim 12, wherein the determination component is configured to:determine the presence state as being indicative of an HDMI sourcedevice not being present based on a voltage value measured by thevoltage measurer when the circuit switch is closed.
 16. The system ofclaim 9, further comprising an isolation circuit configured to: isolatethe voltage divider from temperature variations in the signal sourcedevice; and provide a representation of the electrical signal to thevoltage divider, wherein the representation does not includetemperature-induced variations of the signal source device.
 17. Thesystem of claim 9, wherein the system is one of an HDMI switch that isconfigured to operate as an HDMI sink, or a television.
 18. A systemcomprising: a resistor-capacitor (RC) circuit that includes a resistorwith a resistance and a capacitor with a capacitance approximately equalto combined capacitances of an HDMI sink device comprising the RCcircuit, an HDMI source device, and an HDMI connector therebetween; asignal source device configured to provide an electrical signal to thecapacitor; a voltage measurer configured to measure a voltage of thecapacitor while the capacitor is charged by the electrical signal; and adetermination component configured to: determine an effective value ofthe capacitance; and set a divider capacitance value of a first voltagedivider capacitor of a voltage divider circuit based on the effectivevalue, a second voltage divider capacitor of the voltage divider circuithaving a capacitance approximately equal to the effective value.
 19. Thesystem of claim 18, wherein the voltage divider capacitor comprises acapacitor bank that includes a plurality of bank capacitors; and whereinthe determination component is configured to set the divider capacitancevalue by configuring one or more of the plurality of bank capacitors,having a combined capacitance equal to at least ten times the effectivevalue, as usable by the voltage divider circuit.
 20. The system of claim18, wherein the determination component is configured to determine theeffective value based on a representation of the effective value after acharge time has elapsed.